The use of human waste as a fertilizer for growing plants has been practiced in
China and other Asian countries for centuries. Unfortunately, these practices were
unsanitary, produced foul odors and, in some cases, led to the spread of diseases.
For these reasons, precautions are necessary whenever human waste is used as a fertilizer.

Beginning in
the early 1970s, the National Aeronautics and Space Administration (NASA) conducted
controlled studies using hydroponic techniques to grow food plants using human waste
(urine and feces). These new growth methods overcame the deficiencies of the Asian
practices by eliminating foul odors and direct human contact with untreated waste.

For long-term
space habitation, it is necessary to internally recycle human waste to produce food crops
and potable water and to purify and revitalize the air. NASA's research findings
quickly found applications on earth through the use of plants to treat wastewater in many
small towns and communities. Today, this method is known by a variety of terms,
including constructed wetlands, artificial marshes, rock/reed filters and
phytoremediation.

An example of one of NASA's first operational
systems to treat domestic wastewater is shown below. (See Fig. 1) This
environmentally-friendly system has been in operation since 1975. Through the years,
further developments have been made in the technology. One of the latest system's is
located in Walnut Cove, North Carolina. (See Figs. 2 and 3)